In recent years with the advent of mega-retailers and mass merchandizing, packaging has rapidly evolved. Today, more than ever, packaging is an extension of the marketing effort and product differentiation is often more important than the product itself. Thus product differentiation through enhanced printed graphics on the packaging is critical.
In the paper industry, the term "paperboard" is generally considered to include container board, such as corrugated boxes and linerboard, as well as boxboard, which includes beverage carriers, cereal boxes, milk cartons, small folded boxes, and the like. It has been recognized that sharp, precise graphics cannot be obtained when printing directly on paperboard products, due to the fact that the paperboard printing surface is relatively rough or uneven, as compared with clay coated paper. Further, paperboard normally has a grey or brown color, and printing directly on the darker color of the paperboard will tend to distract from the resolution of the graphs. To meet the demand for improved graphics, there have been attempts to use white packaging substrates produced from bleached pulp. While the white substrates provide enhanced printing surfaces, as compared with the normal brown and grey paperboard, the white paperboard is considerably more costly to produce and lacks the strength of an unbleached pulp substrate. Further, paperboard is relatively thick as compared to publication paper and cannot be printed through use of the modern high speed printing processes that are used for paper printing.
Beverage carrier, which is a type of paperboard, is designed to contain beverage cans in six-packs, twelve-packs, cases, or the like. As the beverage cans have considerable weight, it is important that the beverage carrier have high tear strength. The typical beverage carrier is a two-ply product, generally consisting of a base ply of virgin Kraft formed from long soft wood fibers, which provide the increased tear strength, and an outer or top ply, generally formed of shorter fiber hardwood. The top ply typically receives a clay coating and graphics are then printed on the clay coated top ply. The printed sheet is then die-cut into sections and each section is folded and glued into the shape of a box or container to subsequently receive the beverage cans.
Due to the relatively rough surface of the coated paperboard, as compared to clay coated paper, the printed graphics do not have the fine or sharp resolution compared to graphics printed on paper. Further, it is difficult to produce the clay coated paperboard. Because of the dark color of the substrate, the clay coating must be thick enough to mask the color, but if the clay coating is too thick, it may crack and adversely effect the printed graphics.
A further problem in the production of beverage carrier is that the printing cannot be done on high speed web offset presses as with paper, so that less sophisticated, lower speed printing equipment must be employed.
Thus, there has been a distinct need for paperboard packaging having enhanced graphics.